Scraper apparatus for centrifugal evaporators



Feb. 20, 1951v ZAHM SCRAPER APPARATUS FOR CENTRIFUGAL EVAPORATORS Filed NOV. 5, 1948 INVENTOR. GEORGE G. ZAHM may Patented Feb. 20, 1951 S CRAPER. APPARATUS FOR CENTRIFUGAB.

EVAPORATORS George. G. Zahm, Buffalo, N. Y..,assignor to: The: Hurd Corporation, New York;v N. Y.,a corporation of Delaware Application November 5, 1948", Serial No; 58542 4 Claims. (Cl. 159-45) This: invention relates to certain new and use ful improvements in apparatus for concentrating liquids and, more particularly, liquids containing organic substances which would be impaired if the; liquid were subjected to a high temperature for a-consideraole period of time.

Itiis the primary object of this. invention to provide. apparatus for'treating organic solutions and colloidal liquids, whereby the liquid content inithesamemay be reduced quickly and economioallyand without-impairing the chemical constituency, taste, or; quality of the solutions or liquids.

It is a further-objectofthe present invention to=provide apparatus of the type and forthe purpose-stated in: which entrainmentiis substantially eliminated;

Itisa: further" object of this invention to pro vide means for causing liquidszof the type stated as travel over aheat exchange surface under vacuum at'high velocity, in a relatively thin film, andiwithout'building up a static coating'on the heat'exchangesurface. The. aboveaand' other objects will become more fully apparent from the following specification which; by way of illustration ratherthan limitatlon, sets forthpreferred processes and preferred forms of apparatus constituting embodiments of the present: invention, the scopeof which is defined intheappended claims.

In: the accompanying drawing:

Figure 1 is afragmentary vertical sectional view of a preferred form of apparatus forpractising myinvention;

Figure 2 is a transverse sectionalview alongline; 2-2of Figure 1;

Figure-3 isa fragmentary sectional view show ing, thescraper blades in extended position; and:

Figure 4 is atop view.

Inits. general organizationithe. preferred form of. apparatusshown in: the: drawings comprises. apreferably cast iron base housing I having a eentrally depressed gear box12 provided in its bottom wall with a step-bearing}. Welded :01 otherwise. secured upon the face of the housing Lin closure iorming, disposition across the top of, the gear box 2, ,is an .upstanding'basering 4 having: a ver tical shaftebearing; 5. axially aligned with. the;-

stepebearing 3i andaround its upper peripheral marginthe base ring 4 isintegrall provided with ax. diametrally enlarged upwardly extending colla: 6. Shrunk or otherwisesuitably secured in. the base ring 4 and extending upwardly there from. inconcentric relation to the shaft-hearing iris .a-cylindrical column preferablyconstructed of copper or other suitable material, having a high co-efficient of heat conductivity; and provided at its upper end with a peripherical'ly flanged head ring 8 having a plurality of uniformlyv spaced swingable. wing bolts to for retentive engagement in complementarily located peripheral slots 5 formed in a removable cap or dome 9 preferably of cylindrical form and including a horizontaltop wall i 0, which is,. in. turn, provided with a depending shaft-bearing, ll aligned axially with theshaft-bearing 5.. There is lodged in the upper part: of. the: shaft-bearing ll a: packing-glands;

Surrounding. the column '1 and. affixed; at. its lower: end in thecollar Bis a cylindrical jacket or shell; I2, At its-. upperend the shelliz issecured in a .closure-collarlii mounted around the column isomewhat below the head ring 8, thusformin around. thexcolumn: I. an annular jacket space. M. which. is. adapted to receive steam or. other heating medium for heating thecolumn I; The steam or other; heating agent is preferably supplied to this jacket. space M by means of a steam supply pipe lifixed in and extending through the shell l2adjacent: its. upper: end,,the. excess steam and water. of; condensationbeing withdrawn from the lower endof the'jacket space M by a discharge pipe. [.6 threaded. through the collar 6.

Rotatably mounted at its lower end in the step-hearing 3, and projecting upwardly through the bearing 5, is a vertical shaft I! provided along the portion of its length within the gear box 2 with suitable driving'gears. l8, l9, whichyare conventionally connected to a prime-mover (not. shown). At its upper end, the shaft ll isconnected by means of a spline collar 28 to a head 2| rigidly mounted in the lowerv end of a cylindrical impeller tube 22 of substantially smaller dia metrical size than the column B and extending cc-axially upwardly therethrough into the dome At its upper end;,.the tube 22, is provided with a. radial double-race ball-bearing 2,3 concentric, with the shaft-bearing I]. Erojecting inwardlyat the lower end of the ring 8 1s an annular horizontal partition-plate 24 centrally bored and provided with a packing ring 25 for gland-wise engaging the'tube 22. Within the, column 1, thetuoe 22 is provided with equally spaced vertical lines ofv apertures 25. Abovethe partition-plate 2d, the tube 22 is further provided with a plurality of circumferentially spaced apertures b, so that the dome Q connects directly with the in-- terior of the tube 22, but does not'communicate directly with the annular vapor space between the outer face of the tubezz and the inner face. of column I.

Welded to the outer face of the impeller tube bearing 38';

22 just ahead of each vertical line of apertures 26 (reference being had to the direction of rotation of the impeller tube 22 as shown by the inner arrow in Figure 2) are pairs of diametrally opposed impeller blades 21, 21. It should be noted ing through the column 7 into this head space a:

is a supply-line 28 bent over at its inner end so as to discharge the stream of the incoming liquids against the inner face of the column 1. Finally, the column 1 is provided with a vacuum line 29 which extends throughrthe head ring 8, and a liquid discharge line 30 which extends through the base ring 4, the lines 29 and 3!! connected; respectively,to conventional high vacuum equipment and liquid storage or pumping equipment (not shown). 7

Projecting downwardly through the packinggland a and the shaft-bearing ll, concentrically within the impeller tube 22, is a shaft 3|, its lower end terminating above the upper end of the shaft I! and resting upon a compression spring h set axially into and projecting upwardly from a suitable spring-retaining recess r formed centrally in the upper end-face of the head 2|. The shaft 3| is provided along its length within the impeller tube 22 with a plurality ofdiametrically reduced portions 32 for receiving the yoked ends 1/ of pairs of oppositely extending radial pivot arms 33. Said arms 33 extend through aligned apertures 34 in the'wall of the impeller tube 22 and are pivotally mounted, as at 2, upon the blades 21 and integrally provided with downwardly extending short crankarms 35, the lower ends'of which, in turn, are pivotally connected to ears 36 projecting from the inner vertical margm of elongated scraper blades 31. Said scraper blades-3l are positioned to abut surfacewise in a sliding manner against the rearward surfaces of said "impeller blades 2'! (reference being had to the direction of motion of said impeller blades as shown by the arrow in Figure 2) by means of support pins d which are mounted on the impeller blades 27 and extend through angular slots c formed in the scraper blades 3'! and being so located that the scraper blades 3? will, in retra'cted position, have their outer vertical margin disposed inwardly of the outer vertical margin of the impeller blades 27.

The upper end of the shaft 3| is provided with a collar 38 provided upon its upper surface with a cap-like thrust-bearing 38' and containing therebetween a conventional ball and ball-retainer assembly (2; Formed upon the surface It of the dome 9 is'an upwardly extending radially slotted lug 3'9 offset from the aperture of the shaft-bearing H for rockably supporting a lever 68 provided at its. outer extremity with a conventional handle. At its inner end, the lever 48 is provided with a yoke ll, which extends half around the shaft fii-"and bears, at diametrally' opposite points, under and against the under face of the In operation, a stream of liquid is admitted through the supply pipe 28 and permitted to fiow down by gravity over the inner face of the column I while the latter is externally heated by admission of steam to the jacket space [4. As the liquid flows downwardly a centrifugal motion is im- 4 parted to it by the impeller blades 21 in the formation of a thin tubular film against the inner face of the column 1.

During its flow from the supply line 28 to the discharge line 30, the stream of liquid is subjected to high vacuum and a substantial portion will pass ofi as vapor through the apertures, as diagrammatically indicated by the outer arrows in Figure 2, the vapor flowing upwardly through the tube 22 and the apertures is into the dome 9, thence into the vacuum line 29. The clearance between the outer edges of the blades 2'! and the walls of the column '3 permit portions of the liquid to escape from the influence of the blades 2l-and form a thin film extending from the rear side of each blade to the front of the next following blade 21.

The shaft 3! is rotated by the rotation imparted to the scraper blades 31 from the impeller blades 27. During the operation of the apparatus, it is necessary periodically to remove the thin film which has formed on the walls of the column I to prevent said film from hardening thereon and thereby partially insulating the inner part of the column 1 from the heat in the jacket I2. To accomplish this purpose, the lever arm fill is lowered, freeing the shaft 3i for downward movement, which is caused by the scraper blades 37 moving outwardly through centrifugal action. In moving outwardly, the scraper blades 31 also move upwardly as the support pins d are slid to the inner lower endsof the diagonal slots 0, the length of the slots c thus controlling the amount of movement. This upward component of movement of the scraper blades 3'! causes a depressing of the inner end of the pivot arms 33 through the action of the link 35, whereby the shaft 3'l. ispulled downwardly. Thereby extended, as may best be seen in Figure 3, the outer vertical mar-- gins ofthe scraper blades 3? project beyond the outer, vertical margins of the impeller blades 21 into contact with the walls of the impeller tube 22, lightly scraping said walls as the impeller tube 22 rotates and thereby removing anyfilm which tends to form thereon. It should be understood that changes and modifications both in the methods as well as in the form, construction, arrangement, and combination of the several parts of the apparatus for evaporating or concentrating liquids may be made and substituted for those herein shown and described without departing from the nature and principle of the present invention.

Having thus described my invention, what I claim and desire to secure by Letters Patentis:

1. Apparatus for concentrating liquids comprising a steam-jacketed cylindrical column, a tubular member rotatably mounted co-axiall'y within the column and having a plurality {of apertures opening into its interior, a plurality of radially extending blades rigidly mounted on, and

prising projecting outwardly from the tubular member; a shaft rotatably mounted co-axially within the tubular shaft, pivot arms extending radially out wardly from said shaft through apertures in the walls of said tubular member and rockably secured to selected ones of said blades, links integral with the outer ends of said pivot arms", and scraper blades operatively fixed to the outer ends of said links and means for reciprocating said shaft whereby the scraper blades are moved outwardly into scraping contact with the inner tubular impeller rotatably mounted co-axially within the column, said impeller having a plurality of apertures opening into its interior, a plurality of radially extending blades mounted on and projecting outwardly from the impeller, a shaft rotatably mounted co-axially within the impeller, said shaft being spacedly provided with diametrically decreased portions, pivot arms extending radially outwardly from said diametrically decreased portions of said shaft through apertures in the walls of said impeller and being rockably secured to selected ones of the blades, links integral the outer ends of said pivot arms, and scraper blades operatively aifixed to the outer ends of said links, said scraper blades being parallel with and abutting surface-wise against said impeller blades and means for reciprocating said shaft whereby the scraper blades are moved outwardly into scraping contact with the inner wall of the column.

3. Apparatus for concentrating liquids comprising a steam-jacketed cylindrical column, a tubular impeiler mounted coaxially within the co umn, a plurality of radially extending blades mounted rigidly on and projecting outwardly from the in'lpeller, said blades having their outer vertical margins in spaced relation to the inner face of the column and being arranged in diametrically opposite pairs, said tubular impeller having a plurality of first apertures and second apertures opening into its interior, said second apertures being arranged in two vertically aligned rows which are substantially diametrlcaly opposite to each other and are respectively adjacent to diametrically opposed blades, a shaft mounted coaxially within the impeller, means for permitting the impeller to rotate relatively to said shaft while the shaft remains substantially stationary, said shaft being provided with spaced diametrically reduced portions, pair of oppositely extending pivot arms operativey engaged at their inner ends within the diametrically reduced portions of said shaft and each projecting at its outer end through one of said second apertures and being pivoted upon the particular blade adjacent to such aperture, downwardly extending crank arms integral with said pivot arms, scraper blades pivotally connected to the crank arms, said scraper blades being parallel to and abutting surfacewise against said impeller blades, said scraper blades being provided with a plurality of spaced inwardly and downwardly extending slots, support pins projecting from said impeller blades for slidable cooperation with said slots, and mechanical means for imparting to said shaft a re-. ciprocating motion while rotating whereby the outer vertical margin of the scraper blades may be moved outwardly beyond the outer vertical margins of the impeller blades into scraping contact with the walls of said column.

4. Apparatus for concentrating liquids comprising a steam-jacketed cylindrical column, a

0 Number 6 tubular impeller mounted coaxially within the column, a plurality of radially extending blades mounted rigidly on and projecting outwardly from the impeller, said blades having their outer vertical margins in spaced relation to the inner face of the column and being arranged in diametrically opposite pairs, said tubular impeller having a plurality of first apertures and second apertures opening into its interior, said second apertures being arranged in two vertically aligned rows which are substantially diametrically opposite to each other and are respectively adjacent to diametrically opposed blades, a shaft mounted coaxially within the impeller, means for permitting the impeller to rotate relatively to said shaft while the shaft remains substantially stationary, said shaft being provided with spaced diametrically reduced portions, pairs of oppositely extending pivot arms operatively engaged at their inner ends within the diametrically reduced portions of said shaft and each projecting at its outer end through one of said second apertures and being pivoted upon the particular blade adjacent to such aperture, downwardly extending crank arms integral with said pivot arms, scraper blades pivotally connected to the crank arms, said scraper blades being paraLel to, and abutting surfacewise against said impeller blades, said scraper blades being provided with a plurality of spaced inwardly and downwardly extending slots, support pins projecting from said impeller blades for slidable cooperation with said slots, mechanical means for lowering said shaft while rotating, causing the inner ends of said pivot arms to be moved to a point below the lower walls of said second apertures whereby the pivot arms are rocked upwardly by abutment thereagainst, to pivotally move the scraper blades outwardly beyond the outer vertical margins of the impeller blades into scraping contact with the walls of said column, and spring means bearing against the lower end of the shaft for normally biasing the shaft upwardly and thereby holding the scraper blades in retracted position.

GEORGE G. ZAHM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Rasmussen Feb. 18, 1908 Zahm Jan. 31, 1922 Thompson et a1. June 15, 1926 Martinez Feb. 4, 1930 Heald Dec. 22, 1942 FOREIGN PATENTS Country Date Great Britain Nov. 2, 1938 Number 

